A positive diagnosis of functional (psychogenic) tics

Clinical Neurophysiological Evaluation for Simple Motor Tics

Objective

To demonstrate the usefulness of neurophysiological evaluation to distinguish simple motor tics and functional myoclonus.

Methods

Careful clinical assessments, multichannel surface EMG, and EEG-EMG jerk-locked back-averaging were performed.

Results

Urge to move and ability to voluntarily suppress the movement were reported. EMG bursts showed variable duration and triphasic pattern of the antagonist muscles mimicking voluntary movements. Only the late component of the Bereitschaftspotential (BP2) was present prior to the involuntary movement onset.

Conclusion

Combination of the isolated late BP, premonitory urge, and suppressibility leads to the diagnosis of simple motor tics rather than functional myoclonus.

Significance

The physiological approach in addition to careful clinical assessment is helpful to support the diagnosis of tic.

Cranial functional (psychogenic) movement disorders

Functional (psychogenic) neurological symptoms are frequently encountered in neurological practice. Cranial movement disorders--affecting the eyes, face, jaw, tongue, or palate--are an under-recognised feature of patients with functional symptoms. They can present in isolation or in the context of other functional symptoms; in particular, for functional eye movements, positive clinical signs such as convergence spasms can be triggered by the clinical examination. Although the specialty of functional neurological disorders has expanded, appreciation of cranial functional movement disorders is still insufficient. Identification of the positive features of cranial functional movement disorders such as convergence and unilateral platysmal spasm might lend diagnostic weight to a suspected functional neurological disorder. Understanding of the differential diagnosis, which is broad and includes many organic causes (eg, stroke), is essential to make an early and accurate diagnosis to prevent complications and initiate appropriate management. Increased understanding of these disorders is also crucial to drive clinical trials and studies of individually tailored therapies.

Neurologic diagnostic criteria for functional neurologic disorders

The diagnosis of functional neurologic disorders can be challenging. In this chapter we review the diagnostic criteria and rating scales reported for functional/psychogenic sensorimotor disturbances, psychogenic nonepileptic seizures (PNES) and functional movement disorders (FMD). A recently published scale for sensorimotor signs has some limitations, but may help in the diagnosis, and four motor and two sensory signs have been reported as highly reliable. There is good evidence using eight specific signs for the differentiation of PNES from seizures. Recently, diagnostic criteria were developed for PNES; their sensitivity and specificity need to be evaluated. The definitive diagnosis of PNES can be made by recording typical positive features during the spells, and in a low proportion of cases, where the distinction with an organic etiology cannot easily be done, a normal electroencephalogram suggests the diagnosis. FMD diagnosis relies on diagnostic criteria, which have been refined over time and may be supplemented by laboratory tests in some phenotypes. Rating scales for PNES and FMD could be useful for severity measures, but several limitations remain to be addressed.

Functional jerks, tics, and paroxysmal movement disorders

Functional jerks are among the most common functional movement disorders. The diagnosis of functional jerks is mainly based on neurologic examination revealing specific positive clinical signs. Differentiation from other jerky movements, such as tics, organic myoclonus, and primary paroxysmal dyskinesias, can be difficult. In support of a functional jerk are: acute onset in adulthood, precipitation by a physical event, variable, complex, and inconsistent phenomenology, suggestibility, distractibility, entrainment and a Bereitschaftspotential preceding the movement. Although functional jerks and tics share many similarities, characteristics differentiating tics from functional jerks are: urge preceding the tic, childhood onset, rostrocaudal development of the symptoms, a positive family history of tics, attention-deficit hyperactivity disorder or obsessive-compulsive symptoms, and response to dopamine antagonist medication. To differentiate functional jerks from organic myoclonus, localization of the movements can give direction. Further features in support of organic myoclonus include: insidious onset, simple and consistent phenomenology, and response to benzodiazepines or antiepileptic medication. Primary paroxysmal dyskinesias and functional jerks share a paroxysmal nature. Leading in the differentiation between the two are: a positive family history, in combination with video recordings revealing a consistent symptom pattern in primary paroxysmal dyskinesias. In this chapter functional jerks and their differential diagnoses will be discussed in terms of epidemiology, symptom characteristics, disease course, psychopathology, and supportive neurophysiologic tests.

Posttraumatic functional movement disorders

Traumatic injury to the nervous system may account for a range of neurologic symptoms. Trauma location and severity are important determinants of the resulting symptoms. In severe head injury with structural brain abnormalities, the occurrence of trauma-induced movement disorders, most commonly hyperkinesias such as tremor and dystonia, is well recognized and its diagnosis straightforward. However, the association of minor traumatic events, which do not lead to significant persistent structural brain damage, with the onset of movement disorders is more contentious. The lack of clear clinical-neuroanatomic (or symptom lesion) correlations in these cases, the variable timing between traumatic event and symptom onset, but also the presence of unusual clinical features in a number of such patients, which overlap with signs encountered in patients with functional neurologic disorders, contribute to this controversy. The purpose of this chapter is to provide an overview of the movement disorders, most notably dystonia, that have been associated with peripheral trauma and focus on their unusual characteristics, as well as their overlap with functional neurologic disorders. We will then provide details on pathophysiologic views that relate minor peripheral injuries to the development of movement disorders and compare them to knowledge from primary organic and functional movement disorders. Finally, we will comment on the appropriate management of these disorders.